1. Field of the Invention
The present invention relates to a specific slide-screw tuner that includes a transmission line in some media, such as coaxial, slabline, waveguide or microstrip where one or more probes, slugs or tuning elements can move perpendicularly and in parallel to the center conductor. As a probe moves closer to the center conductor, the mismatch at some frequency will increase, while the mismatch decreases as the probe moves away from the center conductor.
The technique of subjecting DUT (Device Under Test) to variable load impedance or variable source impedance with corresponding load slide-screw tuner and source slide-screw tuner, commonly referred to as “loadpull” or “sourcepull”, is used to test transistors for amplifier, oscillator or frequency multiplier applications. The DUT performance typically depends on the impedance seen by the DUT at its input and output ports, so the slide-screw tuners play the important role of creating the desired impedance at each reference plane, impedance that are controllable in amplitude and phase on the source side and on the load side of the DUT.
2. Description of Prior Art
FIG. 1 schematically depicts a perspective view of a loadpull prematch tuner of U.S. Pat. No. 6,674,293 B1. This prematch tuner has two probes (3) and (4) located on the same side of the slabline (2) compared to the center conductor (1).
FIG. 2 schematically depicts a longitudinal cross-sectional view of a loadpull multi-purpose tuner of U.S. Pat. No. 7,135,941 B1 with 3 probes (23), (24) and (25) located on the same side of the slabline (22) compared to the center conductor (21). This loadpull slide-screw tuner has also transversal walls (26) and (27) in order to separate the 3 carriages P1, P2 and P3 that are supporting the probes (23), (24) and (25). This view demonstrates that carriages P1, P2 and P3 have a longitudinal width which is much bigger than the longitudinal width of the probes (23), (24) and (25). As it is noticeable on this figure, there is a physical impossibility to put the 3 probes closer by reducing L1 and L2 because of the longitudinal width of carriages P1, P2 and P3. This implies a decrease of performance for VSWR/Gamma due to the losses added by a longer propagation along the transmission media. The higher the frequency, the bigger the losses.
FIG. 4 schematically depicts a perspective view of a loadpull slide-screw tuner of U.S. patent application Ser. No. 11/468,433 that depicts a transmission media composed of two parallel slabs (41) and (42) surrounding a center conductor (40). Probe (44), tuning element of the slide-screw tuner, is located on one side of the slabline, the other side of the slabline being terminated with a ground plane (43). Again, one side of the slabline is terminated with a ground plane making it impossible to insert a tuning element on the opposite side of the slabline by design.
FIG. 3 schematically depicts a longitudinal cross-sectional view of a loadpull slide-screw tuner with a transmission media (31), a carriage (32) supporting a probe (34) sliding along the transmission media on a rail (33). A carriage counterweight (35) is located on the other side of the transmission media. This carriage counterweight disables the possibility to access the opposite probe side of the transmission media by design.